Nations and Covenants
A modern nation state cannot make a covenant with God, because there is no one who can make a binding commitment to him on behalf of all the people. A dictator can bind himself, but he cannot bind the people he controls. A democratically elected leader cannot speak for everyone in the nation, because a substantial part of the population will have voted for a different candidate. The elected leader can only bind those who have submitted to them, so they do not have authority to bind everyone in a covenant.
People living within a nation state can make a covenant with God and be born again into the Kingdom of god. However, they can only bind themselves and their children. They cannot bind the rest of the people living within their nation.
When Israel made a covenant with God, it was not a nation state. It consisted of a twelve tribes made up of many families and sub-tribes. The heads of the families and tribes had authority to agree to covenant with God on behalf of their families and tribes. Unfortunately the covenant they made is now obsolete.
An upgrade to a far better covenant is now available, but in the interim Israel has become a nation state and the tribal and family groupings that made the original covenant have disappeared, so they cannot take up the upgrade. The only way to obtain the upgrade is through repentance and faith.